INSECT PESTS 37 



tissues of the boll, and consequently destroys the 

 cotton fibre. In from seven to twelve days the larva 

 changes into the pupa or chrysalis. The pupal stage 

 lasts for about three to five days after which the 

 weevil emerges, and about five days later begins the 

 production of another generation. A very large 

 portion of the weevils are killed by the winter frosts, 

 and it is probable that under average conditions not 

 more than 3 per cent, of those which hibernate sur- 

 vive. Large numbers of the weevils are destroyed by 

 insect enemies, many of which are parasitic. When 

 the young fruits which have been infested by the 

 weevil fall to the ground, the larvae contained in them 

 are very commonly killed by the heat of the sun, and 

 this explains the fact that dry seasons are very 

 inimical to the weevil. In order to control the pest, 

 it is therefore important that the ground should be 

 shaded as little as possible. 



Many attempts have been made to destroy the 

 boll-weevil by means of poisons. It was found at 

 first that such methods usually had little effect and 

 that the results did not justify the expense incurred. 

 Recently, however, good results have been found to 

 attend the application of very finely powdered lead 

 arsenate. 



The pest can be kept in check by observing the 

 following precautions. At the close of the season, 

 the plants should be uprooted and burned, together 

 with all dead leaves and other refuse which could 

 afford a place for hibernation. Attempts should be 

 made to secure an early crop by sowing early-ripening 

 varieties, planting as early as possible, and applying 

 manures when necessary. A good space should be 

 left between the rows of cotton as well as between the 

 individual plants in the row. Another method which 

 has been recommended is to employ a mechanical 

 device for causing the young infested fruits to fall to 

 the ground so that the larvae may be destroyed by 

 the heat or by parasites. 



Special precautions are now being taken to prevent 

 the introduction of the boll-weevil into other countries 

 in imported seed. In several countries, regulation? 



